Federated/decentralized identity is on the roadmap and being worked on - while yes, Matrix conversations and discovery are fully decentralized and federated, each account is still tied to a single homeserver through the domain (e.g. user@matrix.org still depends on the matrix.org homeserver to use their identity)
Arguably none of the alternatives have this quality either but I find it worth pointing out as a requirement for next-generation IM.
Arguably none of the alternatives have this quality either but I find it worth pointing out as a requirement for next-generation IM.